No longer will passers-by wonder what, if anything at all, is being done to salvage the once splendid French Renaissance chateau that has sat decaying and abandoned for more than 25 years on Central Park West between 105th and 106th Streets.

The onetime hospital is undergoing a long-promised massive renovation that will transform it to luxury housing. And it has acquired a sibling, a 26-story condominium tower that is nearing completion at the rear of the property.

Over the years one developer after another has tried and failed to revive the building at 455 Central Park West, with its twin circular turrets, which was the city's first cancer hospital and later a nursing home operated by Bernard Bergman, who was convicted of Medicaid and tax fraud.

With high hopes and generous financing, Daniel E. McLean, president and chief executive of the MCL Companies, a Chicago-based developer, entered the picture in March 2000, when he bought the property for $21 million and began construction. But like numerous predecessors he was forced to halt the work. ''After 9/11 we lost our construction loan and had to wait for about a year to get a new one,'' he said.

His salvation came from a onetime competitor for the site, Columbia University. It has bought the second through 15th floors, which hold 53 apartments that range in size from two to four bedrooms and which will house senior faculty and visiting dignitaries.

''They were the losing bidder when I bought the building,'' Mr. McLean said. ''They wanted to make it half dormitory and half a faculty residence and sell the landmark portion to a private school. But they offered $200,000 less than my bid. When we had a problem, we were approached by a broker who suggested I sell some of the units to Columbia.''

He would not specify how much the university had paid, but said it averaged about $1 million a unit.

The remaining 44 units went on the market earlier this month at prices of $1.35 million to $4.5 million. In addition to the requisite amenities -- generously sized rooms, eat-in kitchens, formal dining rooms, high ceilings, granite countertops, marble bathrooms with showers and tubs big enough for two, and an on-site lap pool -- a panoply of services will be available through the concierge, ranging from catering to passport renewal.

The new building will share a lobby and courtyard designed by David Rockwell with the chateau-style structure, which is being almost totally rebuilt from the inside out. There, each of the 17 condos will have at least one circular room measuring about 38 feet in diameter. Mr. McLean said he expected the units in the original building to sell for $3.5 million to $7.5 million. NADINE BROZAN

A version of this article appears in print on , Section 11, Page 1 of the National edition with the headline: POSTINGS: Central Park West, 105th to 106th St.; Columbia Help Puts Tower at Landmark Site. Order Reprints | Today’s Paper | Subscribe